Determinants of undiagnosed asthma

Background: The conformity between asthma diagnosed in a clinical setting and asthma from an epidemiological point of view has not been much studied. Methods: History, symptoms, and clinical findings in persons with and without a previous physician diagnosed asthma were studied among persons classified as having asthma according to an epidemiological definition. Results: Smoking was more prevalent in persons not diagnosed as having asthma prior to the study (n = 96), than in those with a previous asthma diagnosis (n = 119), (60% vs. 41%, P = 0.006). Positive skin prick test (SPT) was less common (39.6% vs. 58.0%, P = 0.009), lung function expressed as FEV1.0 in percentage of predicted was better (92.1 vs. 85.4, P = 0.018), reversibility to a bronchodilator was smaller (mean reversibility 4.0% vs. 6.2% of predicted, P = 0.003) and symptoms were less frequently reported (P < 0.001) by those who had not a physician diagnosed asthma prior to the study. Conclusion: The asthma diagnosis is often overlooked by the medical profession in patients with mild disease. Furthermore, smoking seems to worsen asthma exacerbations in patients with mild disease.